(CNN) -- A woman in rural Papua New Guinea was bound and gagged, tied to a log and set ablaze on a pile of tires this week, possibly because villagers suspected her of being a witch, police said Thursday.

Her death adds to a growing list of men and women who have been accused of sorcery and then tortured or killed in the South Pacific island nation, where traditional beliefs hold sway in many regions.

The victims are often scapegoats for someone else's unexplained death, and bands of tribesmen collude to mete out justice to them for their supposed magical powers, police said.

"We have had difficulties in a number of previous incidents convincing people to come forward with information," said Simon Kauba, assistant commissioner of police and commander of the Highlands region, where the killing occurred.

"We are trying to persuade them to help. Somebody lost their mother or daughter or sister Tuesday morning."

Early Tuesday, a group of people dragged the woman, believed to be in her late teens to early 20s, to a dumping ground outside the city of Mount Hagen. They stripped her naked, bound her hands and legs, stuffed a cloth in her mouth, tied her to a log and set her on fire, Kauba said.

"When the people living nearby went to the dump site to investigate what caused the fire, they found a human being burning in the flames," he said. "It was ugly."

The country's Post-Courier newspaper reported Thursday that more than 50 people were killed in two Highlands provinces last year for allegedly practicing sorcery.

In a well-publicized case last year, a pregnant woman gave birth to a baby girl while struggling to free herself from a tree. Villagers had dragged the woman from her house and hung her from the tree, accusing her of sorcery after her neighbor suddenly died.

She and the baby survived, according to media reports.

The killing of witches, or sangumas, is not a new phenomenon in rural areas of the country.

Emory University anthropology professor Bruce Knauft, who lived in a village in the western province of Papua New Guinea in the early 1980s, traced family histories for 42 years and found that one in three adult deaths were homicides -- "the bulk of these being collective killings of suspected sorcerers," he wrote in his book, "From Primitive to Postcolonial in Melanesia and Anthropology."

In recent years, as AIDS has taken a toll in the nation of 6.7 million people, villagers have blamed suspected witches -- and not the virus -- for the deaths.

According to the United Nations, Papua New Guinea accounts for 90 percent of the Pacific region's HIV cases and is one of four Asia-Pacific countries with an epidemic.

"We've had a number of cases where people were killed because they were accused of spreading HIV or AIDS," Kauba said.

While there is plenty of speculation why Tuesday's victim was killed, police said they are focused more on who committed the crime.

"If it is phobias about alleged HIV/AIDS or claims of a sexual affair, we must urge the police and judiciary to throw the book at the offenders," the Post-Courier wrote in an editorial.

"There are remedies far, far better than to torture and immolate a young woman before she can be judged by a lawful system."